Macroporous silicon with controllable pore dimensions of 2–10 µm and nanoscale pore walls was produced by wet-chemical etching of pillar-covered substrates. Pillars were formed by irradiation of Si(100) or Si(111) with a femtosecond Ti:sapphire laser in SF₆.  Etching was performed with KOH or N(CH₃)₄OH (TMAH).  When the pillars are removed, the spaces between the pillars are etched to specific shapes dependent upon the orientation of the silicon wafer used. Pores on Si(100) develop into squares with pyramidal bottoms, whereas pores on Si(111) develop into triangles.  These shapes are consistent with the anisotropic nature of etching in KOH and TMAH.  The pores are crystallographically oriented, e.g. the triangles on Si(111) all point in the same direction. The length of a side of the triangle or rectangle is controlled by the mean pillar spacing, which can, in turn, be controlled by the laser irradiation conditions.